In order to enhance cleaning efficiency it is well known to equip a vacuum cleaner with a driven agitator brush that is rotated to beat or brush dirt and debris from the nap of the carpet being cleaned so that the dirt and debris may then be drawn by the vacuum suction into the vacuum cleaner bag for disposal. While a driven agitator brush is very effective for this purpose, it has been found to hinder the cleaning action of a vacuum cleaner when used on bare floors. Specifically, the rotating brush generates a flow of air that tends to push dust, hair balls and other lightweight debris away from the vacuum nozzle and the vacuum suction that would otherwise draw this material into the dust bag. As a result, the cleaning efficiency of the vacuum suffers and the vacuum operator may become flustered and aggravated with the operation of the vacuum-cleaner.
In order to address this shortcoming, many vacuum cleaners now incorporate a shifter mechanism including several carpet and bare floor settings. When the shifter mechanism is positioned on a carpet setting, the agitator brush is engaged and rotated. Conversely, when the shifter mechanism is engaged on the bare floor setting, the drive to the agitator brush is interrupted. Since the agitator brush is not rotating, it generates no air flow and consequently, lightweight debris such as dust and hair balls on the bare floor are not pushed away from the nozzle assembly of the vacuum cleaner. Instead, they are drawn by suction force directly into the vacuum cleaner and eventually the vacuum cleaner bag. In this way, bare floor cleaning efficiency is enhanced.
In order to provide this operation, a number of expensive and complicated mechanical operating designs have been devised. In one such approach, the vacuum cleaner is equipped with two separate motors. One motor functions to drive the agitator brush while the other motor functions to drive the fan for generating the vacuum suction. In this approach, when a shifter mechanism is set to provide for bare floor operation, the motor that drives the agitator brush is deenergized and the brush rotation stops while the motor that drives the fan continues to operate at full speed generating vacuum suction. In an alternative approach, a single motor is provided with a clutch system between the motor and the belt and pulley system that drives the agitator brush. Thus, when the shifter mechanism is engaged on the bare floor setting, the clutch system operates to disengage the motor and the agitator brush so that the brush is not driven.
In still another alternative approach, a two belt system is provided. The two belt system includes one belt connected between the motor drive shaft and a first, constantly driven idler pulley and a second belt connected between the agitator brush and a second idler pulley. When the shifter mechanism is engaged in the bare floor setting, the second idler pulley is operatively disconnected from the first idler pulley and, therefore, neither the second idler pulley nor the agitator brush is driven.
While all of these prior art approaches effectively allow the agitator brush to be disengaged for vacuum cleaning, it should be appreciated that all these designs suffer from a number of drawbacks that prevent any one of them from being an ideal solution to the problem. The two motor system is, of course, relatively expensive to produce. Further, the second motor adds weight to the vacuum cleaner and many users find this added weight to be a discomfort and an inconvenience when manipulating the vacuum cleaner across the floor or carrying it from room to room.
A vacuum cleaner clutch system of the type described is relatively difficult and expensive to manufacture. It significantly increases the cost of the vacuum cleaner and while generally reliable it is an additional mechanical system that from time to time may be the subject of mechanical failure.
Similarly, the two belt system relies upon the utilization of two belts instead of one. It is well known that belts stretch and wear over time and require periodic replacement. Many vacuum cleaner users find belt replacement to be an inconvenient nuisance and the provision of two belts instead of one only adds to this perceived problem.
Perhaps the best solution to this problem to date is disclosed in published Japanese patent application no 57-131420. In this design, a belt driven agitator brush and a displaceable idler roller are provided. When in a first position, the idler roller does not interface with the belt drive. When in a second position, the idles roller disengages the belt from the motor drive shaft thereby allowing the shaft to turn freely and the agitator roller to come to a stop. While this is a more cost effective design than the approaches described above, it still suffers, from some shortcomings. For example, the throw of the shift lever to move between the two operating positions is almost 180.degree.. This is uncomfortable and inconvenient to manipulate.
Accordingly, it should be appreciated that all prior art approaches suffer a number of distinct disadvantages and drawbacks. A need is therefore identified for a new solution to the problem. Ideally, the new solution will allow one to disengage the drive system from the agitator brush when vacuuming bare floors in a user friendly manner and in a cost effective manner without adversely affecting the operating characteristics of the vacuum cleaner or inconveniencing the user in any manner.